1. The Field of the Invention
The present invention relates to methods and apparatus for using polarizing lenses or filters to create the perception of depth when viewing laterally moving objects in two dimensional single image displays. In a further aspect, the present invention relates to the plane of polarization of polarizing filters used to produce the visual depth effects. In a still further aspect, the present invention relates to a method of controlling the movement of objects to create visual depth effects when observers wear glasses with polarizing lenses. The system is suited for motion picture films. The methods and apparatus may also be used for video displays (television, computer displays, video games, etc.) and other types of media.
2. The Prior Art
The prior art includes methods to create the perception of depth in two-dimensional motion picture films and video displays. These methods have been described in or have been the subject of various patents. The prior art often produces one or the other of the following negative side effects:
(1) Reduction or loss of the perception of color. PA1 (2) Dead eye effect wherein observers have the sensation that one eye is not functioning properly.
One class of prior art systems uses two separate shifted images to produce visual depth effects. These systems use special eye wear that transmits one image to the left eye and the other image to the right eye. When the special eye wear is worn by an observer, differences in the relative position of objects as seen by the two eyes produces the perception of depth. Observers viewing the imagery without the special glasses see double images.
The prior art commonly uses color or polarizing filters to separate the two images. Light of the two images are polarized at right angles (90 degrees) to each other. Viewing glasses or spectacles with left and right eye polarizing filters with the plane of polarization at right angles to each other arc used to transmit the image polarized in one plane to the left eye and the image polarized in the other plane to the right eye.
U.S. Pat. No. 4,957,361 to Shaw discloses using spectacles with left and right eye filters that are polarized at right angles to each other to produce the perception of depth when viewing motion pictures with double images that are polarized at right angles to each other.
U.S. Pat. No. 4,630,097 to Marks discloses using spectacles with left and right eye filters that are polarized at right angles to each other to produce the perception of depth when viewing video displays with double images that are polarized at right angles to each other.
Numerous other prior art systems use viewing glasses with lenses polarized at right angles to each other in a similar manner to transmit one image to the left eye and another image to the right eye.
Another method of creating visual depth effects is based on the Pulfrich Effect. This effect is produced by viewing moving objects which appear brighter to one eye than the other. The basic Pulfrich Effect is commonly produced by placing a dark lens or filter over one eye. Objects that move laterally in one direction appear to be farther away from the observer. Conversely, objects that move laterally in the opposite direction appear to be closer to the observer. The basic Pulfrich Effect is a uni-directional motion sensitive depth effect. The relationship between the direction of movement and the perception of depth is dependent upon which eye is covered by the dark lens. When the left eye is covered by the dark lens, objects moving left to right (from the observer's perspective) appear to be farther away. Objects moving right to left appear to be closer. When the right eye is covered by the dark lens, objects moving left to right appear to be closer. Objects moving right to left appear to be farther away.
The apparatus used to produce the basic Pulfrich Effect tends to cause an undesirable side effect. The eye covered by the dark lens receives substantially less light than the other eye. This produces the sensation that one eye is dead or not working. This dead eye effect becomes irritating to observers over time.
U.S. Pat. No. 3,445,153 to Marks is based on the basic Pulfrich Effect. Observers wear special lenses. The lens over one eye reduces the light normally received by the cones (photopic vision).
Dudley discloses in U.S. Pat. No. 4,131,342 a method of combining the basic Pulfrich Effect with a chromostereoscopic effect. The chromostercoscopic effect is based on the finding that objects of colors towards the red end of the visual spectrum appear closer than objects of colors towards the blue end of the spectrum. The chromostercoscopic effect is very weak. It also restricts the use of colors in objects and backgrounds. U.S. Pat. No. 4,131,342 teaches that the basic Pulfrich Effect is due to a "differential visual time-lag" whereby the human visual system processes a brighter image faster than a dimmer image. Therefore the location of moving objects appears to be different for the eye receiving the brighter image than for the eye receiving the dimmer image. The location of moving objects appears to be more advanced for the eye receiving the brighter image than for the eye receiving the dimmer image. This apparent eye to eye difference in the perceived location of moving objects produces the visual depth effect.
U.S. Pat. No. 4,705,371 to Beard is also based on the basic Pulfrich Effect. Observers wear another type of special lenses. The lenses are intended to reduce the dead eye effect.
U.S. Pat. No. 4,836,647 to Beard discloses alternative colored filters to produce the basic Pulfrich Effect. The colored lenses were designed to reduce the light from television displays more than the light from normal room lighting. The colored lenses were intended to reduce the "dead eye" effect.
The four methods above (U.S. Pat. Nos. 3,445,153; 4,131,342; 4,705,371; and 4,836,647) are all limited by the unidirectional nature of the motion sensitive depth effect. They are all also somewhat prone to the dead eye effect.
U.S. patent application Ser. No. 06/483,564 by Osgood teaches a means to produce a bidirectional basic Pulfrich like effect. U.S. patent application Ser. No. 06/483,564 used objects moving laterally against colored backgrounds or surrounds laterally moving colored objects, and colored viewing glasses. The left lens of the viewing glasses passes from 4 to 20 times as much light of one color (e.g. red) as the right lens. The right lens of the viewing glasses passes from 4 to 20 times as much light of another color (e.g. green). Objects moving laterally against surrounds of the first color, and laterally moving objects of the first color, appear closer to the observer when they move from left to right and farther away from the observer when they move from right to left. Objects moving laterally against surrounds of the second color, and laterally moving objects of the second color, appear closer to the observer when they move from right to left and farther away from the observer when then move from left to right.
The methods of U.S. patent application Ser. No. 06/483,564 allow each eye to receive enough light to reduce or even totally avoid the dead eye effect. However, neither eye receives the full intensity of light across the entire visual spectrum. Therefore observers may perceive a reduction in the color saturation of the images viewed. The directionality of the depth effects is dependent upon the color of the surrounds for laterally moving objects and the color of the laterally moving objects. This limits the choice of colors in the imagery. It may also lead observers to use the colors of the laterally moving objects and the colors of the surrounds for laterally moving objects to predict the direction of the visual depth effects.